Technical Field
The present invention relates to a vehicle lamp having a semiconductor laser element as a light source and, more particularly, to a vehicle lamp for generating a white light by combining a semiconductor laser element and a phosphor.
Related Art
In a vehicle lamp such as an automobile headlamp, it has been attempted to use a laser diode (LD) in place of a light emitting diode (LED) (see Patent Document 1). Since an LD light source has a high light-conversion efficiency and a small light-emitting area, the LD light source is advantageous for miniaturization of the lamp. In the vehicle lamp using the LD light source, a laser light, e.g., a blue laser light is irradiated from an LD element to a phosphor that is a wavelength-conversion element, a light, e.g., a yellow light is emitted due to excitation of the phosphor, and the blue laser light and the yellow light are mixed, thereby emitting a white light.
Laser light is a high-energy light having strong directivity. When being used as a light of a vehicle headlamp or the like, as described above, the laser light hits the phosphor and is scattered. In this way, the laser light is converted into a white light which is suitable for road surface irradiation and has a suitable energy. When the laser light does not hit the phosphor sufficiently, high-energy laser light is reflected in the reflector and is irradiated to a pedestrian, a vehicle or a road surface or the like in front of a vehicle. In order to avoid such a situation, the phosphor is strongly fixed to a mounting body in order to prevent the detachment or damage thereof.
In order to avoid the direct irradiation of high-energy laser light, various methods have been taken that include a method of strongly fixing the phosphor to the above-described mounting body such that the phosphor is not detached or damaged. However, although possibility of occurrence is extremely low, it is difficult to assert that the detachment of the phosphor is completely avoided. In order to confirm (in other words, in order to detect abnormality) that the phosphor is properly operated, i.e., that laser light hits the phosphor and is properly scattered, typically, a light detector is installed at a required place of an optical path to measure an amount of energy (intensity of light) or wavelength of light, thereby checking the presence or absence of abnormality. When abnormality is detected and it is determined that high-energy laser light is radiated without hitting the phosphor, the phosphor is estimated to be detached or damaged for some reason, thereby stopping the driving of the laser element.
In addition to this, there has been suggested that high-energy laser light is prevented from being reflected to the front from a reflector by forming a through hole penetrating the reflector or an escape hole (reference numeral H2 in Patent Document 1) in the reflector that is hit by laser light in an abnormal situation and thereby allowing the laser light to be escaped to the outside of the reflector.    Patent Document 1: Japanese Patent Laid-Open Publication No. 2014-180886
However, there is a problem that high-energy laser light is reflected in the reflector and is directly irradiated to the front when the light detector is not present, the light detector is damaged or the light detector is not quickly operated.
Further, in the case of forming the above-described escape hole, there is a disadvantage that a portion of the white light reaching the reflector in a normal driving is wasted. Furthermore, there is a possibility that the laser light escaped to the outside of the reflector in an abnormal situation is reflected multiple times for each member, and finally, high-energy laser light is irradiated to the outside of a lamp chamber.